Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various material layers using lithography to form circuit components and elements thereon. Many integrated circuits are typically manufactured on a single semiconductor wafer, and individual dies on the wafer are singulated by sawing between the integrated circuits along a scribe line. The individual dies are typically packaged separately, in multi-chip modules, for example, or in other types of packaging.
A read-only memory (ROM) device structure is a nonvolatile semiconductor memory device which is widely utilized in digital electronics applications. The data stored in the ROM device structure can be retained permanently even after the power is turned off.
Although existing ROM devices and methods of fabricating ROM devices have generally been adequate for their intended purposes, they have not been entirely satisfactory in all respects.